In recent years, there has been an increasing demand to reduce the thickness of display devices represented by television sets and monitors for personal computers for saving installation space. As a display device capable of being made thin, the development of liquid crystal displays (LCD) has been aggressively pursued in which a display device is composed of a plasma display device (PDP (Plasma Display Panel) device), a field emission display (FED), a back light, and thin liquid crystal panel.
The PDP device is an imaging device using a plasma display panel (PDP) as the light emitting device. The PDP is so configured as to emit light in the visible region by exciting a phosphor which is arranged in the phosphor layer in the micro discharge space using ultraviolet light as an excitation source generated in a negative glow region in the micro discharge space containing a rare gas (it is in the wavelength region from 146 nm to 172 nm when Xe (xenon) is used as the rare gas). The PDP device uses this emitted light by controlling the intensity and color thereof. Therefore, phosphor becomes very important as a main component for constituting a PDP device.
As documents including this kind of material and technology, for instance, JP-A-2002-332481 (patent document 1), JP-2003-142004 (patent document 2), ┌PHOSPHOR HANDBOOK┘ CRC Press 1998, Edited by Shigeo Shionoya, William M. Yen, Part III Chapter 10 pp 623-636 (non-patent document 1), and “G. Blasse, W. L. Wanmaker, J. W. ter Vrugt and A. Bril, Philips Res. Repts. 23, p 189˜200 (1968) (non-patent document 2)” are provided.